This invention relates to an easy open end and, in particular, to a metal can end of the so-called xe2x80x9cfull aperturexe2x80x9d type, having a circumferential score which enables a circular panel of the end to be removed for access to a product within the can.
An easy open can end having a full aperture easy opening feature typically comprises a seaming panel, a chuck wall and a countersink joining the chuck wall to a central panel. A circumferential score is provided adjacent the countersink and a metal tab is rive ed to the central panel so that its nose is positioned above the score. One example of such a can end is described in French patent application number 2687372.
In a can end having such a circumferential score, the nose of the metal tab pierces the score directly when the handle is lifted. Breaking the score takes place in three stages. Firstly, by lifting the handle, the score tears or xe2x80x9cpopsxe2x80x9d and an initial arc is severed as the tab is lifted to the position where the tab is perpendicular to the end. By pushing the tab over in a second action until it meets the peripheral chuck wall of the end, the initial score tear is propagated. In the third stage, the tab and end panel are pulled out away from the can body so that the end peels away from the can body.
By breaking a greater arc in the second stage of opening, usually defined in terms of the length of the chord joining the ends of the initial arc, the tear force required to remove the central panel in the final stage is reduced. However, the maximum chord length achievable may be dictated by various factors, including the maximum tilting of the tab to meet the chuck wall. Furthermore, in order to achieve a larger chord length, the force required for the first stage of opening, i.e. the xe2x80x9cpopxe2x80x9d force, may exceed acceptable values. The present invention seeks to reduce tear force requirements by achieving a large chord length without adversely affecting the pop force requirements.
According to the present invention, there is provided a metal can end comprising a central panel; a circumferential score; and a tab fixed to the central panel adjacent the score with its longitudinal axis along a radius of the end such that, when the tab is raised, an arc of the score is broken, the arc having a chord joining its ends; characterised in that the grain or the metal end has an angle which is xc2x115xc2x0 to 60xc2x0 to the longitudinal axis of the tab.
When the tab is raised, an arc of the score is broken, the arc having a chord joining its ends. A tangent in the plane of the end and at one end of the chord is substantially parallel to the grain of the end.
According to another aspect of the present invention, there is provided a metal can end comprising a centre panel, a circumferential score and a tab fixed to the panel adjacent the score such that, when the tab is raised, an arc of the score is broken, the arc having a chord joining its ends; characterised in that the metal of the can end has a grain which is parallel to a tangent to the can end in the same plane as the can end and at one end of the chord.
In a preferred embodiment, the grain is between +/xe2x88x9210xc2x0 to the tangent to the can end at one end of the chord.
The score may have a residual which is lower at the end of the chord having the tangent to which the grain is aligned than at the other.
According to a further aspect of the present invention, there is provided a method of making a can end such as is described above, the method comprising a) cutting blanks from a metal sheet; b) forming the blanks into end shells; c) lining the shells; d) feeding the shells into a conversion press; e) forming a score (10) and f) fixing a tab to the shell; characterised by, between steps d) and e): determining the orientation of each shell; lifting each shell and turning it until the shell has its grain substantially parallel to a predetermined tangential position; and characterised in that step f) is carried out such that the longitudinal axis of the tab is xc2x115xc2x0 to 60xc2x0 to the grain.
A preferred embodiment of the invention will now be described, by way of example only, with reference to the drawings, in which: